Fabrication of Glass mat Thermoplastic composite by Needling Punching Process

Tsutomu SETO1,2, Yuying DONG3, Yuqiu YANG3*,

Zhiyuan ZHANG4,Ryo MARUI5,Takayuki SAKAI6,Hiroyuki HAMADA1, 1:Kyoto Institute of Technology, Kyoto,Japan, 2:Matsuura Co.,Ltd,3*: Key Laboratory of Textile

Science &Technology,Ministry of Education, College of Textiles, Donghua University, China, 4: Daiwa Itagami Co, Itd 5-32, Kawaharacho, Kashiwara-city, Osaka, Japan

5: Marui Textile Machinery Co.,Ltd 6:Tokushima University, Japan (*amy_yuqiu_yang@hotmail.com)

Abstract As well known, non-woven materials, because of

simple preparation Process and wide range of applications, attract more and more attention. Needle punch process is widely used in textile area and expresses excellent performance. The introduced thickness-direction fibers via needle punched process play an important role to reinforce the composite in thickness which can minimizes delaminating problems. In this research, short glass fiber mat and plastic fabric produced by PP were used to fabricate thermoplastic composite through hot press process. The glass mat and thermoplastic mat were punched before hot pressing. This research mainly includes two parts, that is, effect of composites in different molding temperature on tensile properties, and the influence of composites in different needling density on tensile properties. Finally, cross sectional observations of molded sample were carried out using a scanning electron microscope (SEM), and the fracture characteristics were evaluated.

Introduction

For energy saving and carbon dioxide restraint, light weight materials is demanded in automobile, railway and aviation area. The carbon fiber reinforced plastics (CFRP) was useful and widely discussed as a representative fiber reinforced plastics (FRPs). However due to the difficulty of FRPs molding process, the cost is relatively higher which has limited the application of FRPs. The fiber reinforced thermoplastic is considered regarded as one of the techniques to reduce production cost. The hot press molding method is suggested as one of the techniques to produce fiber reinforced thermoplastics FRTP[1] 。 Various methods were proposed to make prefabricating materials. For example, reinforced fibers (carbon fibers or glass fibers) were made to sheet by papermaking method [2], and reinforced fibers mat insert into the matrix mat. Both of these method haven’t yet used for production in large quantities.

Needle punch process was widely used in textile area provided remark performance. The introduced thickness-direction fibers via needle punched process play an important role that provides excellent z-directional properties that minimizes delamination problem. Sung Ho Lee and Tae Jin Kang [3] studied the

effect of changes in fiber structure on the mechanical properties of nonwoven composite with different punching densities. It was found after needle punch process the tensile strength and mode-I interlaminar fracture toughness of nonwoven composite was increased with increasing punching density due to the increased fiber entanglement. The flexural impact, fatigue and wear properties were decreased with punching densities because of the damage to fiber during the punching process which resulted in the reduction of fiber length.

At current study, the thermoplastic resin was polypropylene (PP) to be used as matrix for composite fabrication. Needle punched process was introduced to fabricate glass mat/thermoplastic materials. And then, hot press process was conducted to fabricate composites. Tensile test was conducted on four kinds of specimens which were produced in different molding conditions. Scanning Electron Microscope (SEM) was used to examine the fracture characteristics of failure specimens.

Materials and Experiment

1.1 Needle punched process

Needle punched nonwoven materials principally comprise fibers in the in-plane direction but some of the fibers are also orientated in the thickness direction. Generally, these nonwovens are produced by repeated penetration of a set of barbed needles on the fibrous web for converting it into coherent and self-locking materials. When the needle-punched nonwoven fabric used in composite fabrication, the thickness direction fibers can reinforced the composite in thickness which can prevent delaminating effectively.

Fig.1 The needle punching machine

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The image of the needle punching machine is shown in Fig.1. The mat was fed in the arrow direction. As the delivery speed up, the needle density of glass mat and PP nonwoven fabric decreased.

1.2 Materials and specimens

The glass mat was made of 50 mm chopped fiber bundles, and PP fibers, which length and diameter is 60mm and 10µm respectively, were used for fabricating mat fabric. These materials were used to be punched before hot pressing. During needle punched process, two layers that the glass mat was set below the PP nonwoven fabric, were punched together. The polymer fibers can penetrate into the glass mat fabrics which is helpful for impregnation glass fibers. And then two kinds of non-woven materials that have different needling density (high density: 40×26/mm2 low density: 35×26/mm2) were produced by changing the delivery speed, photographs depicting are shown in Fig.2.

Fig.2 needle punched material

2.3 DSC test DSC was tested to confirm the thermal properties of

the PP fiber websheet i.e. the matrix. The results are shown in figure 3.It is known that the peak of the melting point was more than 170 ℃ as a result of DSC. Two kinds of sheet were at a molding temperature of 200℃or 230℃，which were used to fabricate thermoplastic composites by through hot pressing（Forming pressure reaches 18MPa, molding time 10 minutes）. The proportion of glass fibers is 35% in weigh.

Fig.3 DSC of the PP fiber websheet

2.4 Tensile Test

The composites were cut into the design size according to Japanese Industrial Standards (JIS K7113 and JIS K7085). The specimens were cut into 200 mm×20 mm×0.8mm; At least three pieces of specimens were repeated. Tensile test was performed by using an Instron universal testing machine cross head speed of 1 mm/min. a strain gauge (KYOWA KFG-10-120-C1-11) was employed to measure the strain of the specimens during the testing process.

Results and discussion

3.1The optical observation

A. High density material at the Fabrication Temperature 200℃

B. Low density material at the Fabrication Temperature 200℃

C. High density material at the Fabrication Temperature 230℃

D. Low density material at the Fabrication Temperature 230℃

Fig.4 Optical observation image of FRTP specimens

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The optical observation results are shown in figure 4. For the four kinds of thermoplastic composites, it is difficult to find big voids in the observation photos. As a result, it is considered that they may have fine tensile property.

3.2 The tensile test results of specimens

There are four kinds of specimens to be tested in tensile test. The Stress-Displacement curves of FRTP are shown in Fig.5.

Fig.5 the Stress-Displacement curve of FRTP

It was found that failure character was substantially similar to the four kinds of specimens, tensile stress was proportional to the displacement before it reached peak of curve. When glass fiber/PP composites were destroyed, the tensile stress was rapidly reduced, and stabilized at a value. The tensile strength of glass fiber/PP composites in 230 ℃ was higher than composites in 200℃. In addition, it was discovered that tensile strength of high density material at the Fabrication Temperature 200℃ had a big deviation. As a result, more specimens were tested in tensile texting. It was found that tensile strength of high density specimens is lower than low density specimens when the molding temperature is 200 ℃ .It was assumed that tensile strength of glass fiber/PP composites was increased with increasing punching density due to more fibers entanglement in the range of certain punching density. In the hot press process, if punching density was too high, the thermoplastic resin can’t impregnate glass fibers easily. Therefore, tensile property of high density materials at the molding temperature 200℃ was poorer than low punching density.

Fig.6 the tensile strength of FRTP

The effect of tensile strength in punching density and fabrication temperature are shown in Fig.6. For fiber reinforced polymer materials, fabrication

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67.78

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200℃ 230℃ 200℃ 230℃

high low

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temperature and connection between fibers and matrix are the crucial factor to determine the mechanical properties of the composite. In this research, it was found that fabrication temperature made an obvious influence on tensile strength of thermoplastic composite when the materials were punched by high density. And as the fabrication temperature increasing the materials has a tendency to have a better performance. It is considered that the composites in high fabrication temperature are beneficial which accelerate resin fluidity, more matrix impregnation glass fibers, and decrease the voids or weakness inside the materials.

3.3 SEM observation The SEM observation of the break side after the

tensile test is shown in figure 7. It is known that the mode of the destruction is destruction of the matrix resin after tensile text. It was found that the surface of glass fibers is very clear. The reinforcement fibers don’t break. In addition, little matrix can be residual on the fibers which means the bonding effect between glass fibers and matrix is not so good. This is also an important aspect to improve the mechanical property of these kinds of materials.

Conclusion 1. Short glass fiber mat and plastic mat produced by PP

were used to fabricate thermoplastic composite through needle punch. After hot compression, glass fiber/PP stampable sheets were fabricated successful.

2. As the fabrication temperature increasing, the material has a tendency to have a better performance due to flowing easily of PP resin.

3. It is considered that it is more convenient to apply needle punched method than papermaking method. it is possible that the method with advanced formativeness is spreaded In further study, these parameters are considered to be

carried out to find the suitable molding methods for FRTP such as the fiber types, plastics fiber types, fiber diameter, fiber length, needle punching density and so on.

References [1]Fujiwara Junkai: Academic Lecture on production and

processing, 2004(5), 173-174, 2004-11-19 (Japanese Version)

[2]Matoba Akira: Japan composite material Journal 19(1),3-7,1993(Japanese Version)

[3]S. Lee and T. Kang Mechanical and Impact Properties of Needle Punched Nonwoven Composites. Journal of Composite materials, 34,816-840,2000

Key words: Needle punch, Glass mat, Thermoplastic, Hot press

Fig.7 SEM observation of failure specimen

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